The present invention relates to an optical system having a shutter assembly therein and, more particularly, to the shutter assembly wherein the shutter drive mechanism is integral with and mounted on the movable shutter.
Some optical systems include a shutter assembly with a shutter that controllably blocks and unblocks the optical path. The shutter assembly usually includes a shutter electromechanical drive and a shutter mechanical drive extending from the shutter electromechanical drive to the shutter. The shutter electromechanical drive may include a solenoid, a DC motor, a stepper motor, or the like for generating a controllable movement. The shutter mechanical drive usually includes a mechanical linkage, levers, gears, or the like, for transmitting the mechanical movement of the shutter electromechanical drive to the shutter.
In a typical configuration, the shutter is pivotably mounted to its support, and the shutter electromechanical drive is mounted close to, but not integral with, the shutter. The shutter mechanical drive extends from the shutter electromechanical drive to a location laterally separated from the pivot point. A movement produced by the shutter electromechanical drive, and transmitted to the shutter by the shutter mechanical drive, causes the shutter to pivot between an open position wherein the optical path is not blocked, and a closed position wherein the optical path is blocked.
This approach is operable and widely used, but it has limitations in certain applications. The shutter assembly is often placed between two other optical elements, such as between two lenses or between a lens and another optical device. When the optical system is miniaturized, it is difficult to miniaturize the shutter assembly with its shutter electromechanical drive and its shutter mechanical drive proportionately. The miniaturized shutter assembly therefore is still relatively thick, bulky, and heavy. Additionally, the shutter mechanical drive may have backlash and a considerable inertia, so that its movement is not as precise or as rapid as might be desired.
There is a need for an improved approach to the shutter assembly used in optical systems and otherwise. The need is particularly acute for miniaturized shutter assemblies used with physically small optical systems. The present invention fulfills this need, and further provides related advantages.
The present approach provides an optical system with a shutter drive mechanism that is integral with the shutter assembly. There is no separate shutter electromechanical drive, and therefore no shutter mechanical drive extending from the shutter electromechanical drive to the shutter. The present shutter assembly is therefore smaller, thinner, and lighter than conventional shutter assemblies. It may also be miniaturized much more readily than the conventional shutter with its drives.
In accordance with the invention, an optical system comprises a shutter assembly, which includes a support, a shutter movable with respect to the support, and a shutter drive mechanism. The shutter drive mechanism includes a first magnet affixed to a first one of the support and the shutter, and a first electromagnet structure affixed to a second one of the support and the shutter and comprising a first-structure first electromagnet. The first magnet and the first-structure first electromagnet are positioned such that activation of the first-structure first electromagnet causes the first magnet to move relative to the first-structure first electromagnet. Accordingly, the shutter, which is typically movable, moves relative to the support, which is typically stationary.
The optical system desirably has an optical path, and the shutter assembly is operable to controllably block and unblock the optical path. By properly locating the first magnet and the first-structure first electromagnet, the shutter may be made to move between a desired open position and a desired closed position. In most cases, the optical system further includes an optical element that interacts with a light beam traveling along the optical path.
It is preferred that the first magnet be a permanent magnet, and that the permanent first magnet be affixed to the movable shutter. The mass of the shutter and its affixed permanent magnet is thereby kept to a minimum, and there are no electrical wires leading to the shutter. The first electromagnet is affixed to the stationary support. In a convenient arrangement, the shutter is pivotably mounted to the support.
The shutter is usually designed either to be normally open or normally closed. To aid in retaining the shutter in the normally open or normally closed position in the absence of any current flow through the first electromagnet, there may be provided a bias structure operable to bias the shutter toward a first position, and the activation of the first electromagnet structure moves the shutter to a second position. The bias may be a spring or another magnet that provides the biasing force. In one embodiment, the core of the first electromagnet may be made of a rod of a soft magnetic material such as a magnetized low-carbon steel. The core acts as a biasing magnet to bias the shutter toward the position of the first electromagnet.
In another approach, the first electromagnet structure may further include a first-structure second electromagnet, wherein the first magnet and the first-structure second electromagnet are positioned such that activation of the first-structure first electromagnet and the first-structure second electromagnet both cause the first magnet to move in the same direction relative to the first-structure first electromagnet. In the usual case, the first-structure first electromagnet and the first-structure second electromagnet are electrically wired such that, upon activation, one attracts the first magnet and the other repels the first magnet. The polarity of the electromagnets may be reversed to cause the first magnet, and thence the shutter structure to which it is attached, to move in the opposite direction.
In its preferred form where it is on the stationary support, the first electromagnet structure lies on one side of the shutter. There may be provided a second electromagnet structure, having a structure like that of the first electromagnet structure, but fixed to the support on the opposite side of the shutter. The two electromagnet structures are arranged to force the shutter to move in the same direction. The result is increased magnetic force applied to the shutter.
Thus, an optical system comprises a preferred shutter assembly including a stationary support, a shutter pivotably mounted upon and movable with respect to the support, and a shutter drive mechanism. The shutter drive mechanism includes a permanent first magnet affixed to the shutter, and a first electromagnet structure affixed to the support facing a first side of the shutter and comprising a first-structure first electromagnet. The permanent first magnet and the first-structure first electromagnet are positioned such that activation of the first-structure first electromagnet causes the permanent first magnet to move relative to the first-structure first electromagnet. The shutter drive mechanism also includes a second electromagnet structure affixed to the support facing a second side of the shutter and comprising a second-structure first electromagnet. The permanent first magnet and the second-structure first electromagnet are positioned such that activation of the second-structure first electromagnet causes the permanent first magnet to move relative to the second-structure first electromagnet in a same direction as the activation of the first-structure first electromagnet. Compatible features discussed elsewhere herein may be used with this embodiment as well.
The present approach thus uses the support and the shutter themselves as the movable components that drive the opening and closing action of the shutter, rather than using a separate shutter electromechanical drive and a shutter mechanical drive. Size, mass, inertia, and potential problems such as backlash are thereby avoided. Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.